1. Field of the Invention
The present invention relates, in general, to the processing of substrates and, more specifically, to process gas injection systems.
2. Description of the Related Art
In semiconductor device fabrication, a substrate or wafer is subjected to a number of processes in order to deposit or remove a layer from the wafer. Many of these processes involve the injection of gases into a reaction chamber containing the wafer. These gases can include, for example, reactive gases injected to deposit a layer on the substrate. In addition, inert gases can also be injected into the reaction chamber to purge reactive gases from the chamber between reactive steps. Injection systems for injecting these gases generally include gas sources (such as gas tanks, bubblers, other liquid and/or solid vaporization devices) connected via piping to injectors which use valves to control the injection of gases into the reaction chamber. Mass flow controllers and valves are adjusted in order to select the type and amount of the desired source gas(es) to inject into the reaction chamber. In addition, the gas injectors in a bank of injectors are normally manually tuned for gas flow uniformity in advance of processing.
Generally, during processing of a wafer in a reaction chamber, if different injector settings are needed, the chamber is shut down and purged in order to adjust the injector valves to the desired setting. This is a time consuming process. Accordingly, rather than adjusting tool settings between process steps, wafers are often processed using multi-chamber process tools (e.g., a cluster tool), where a series of individual chambers are each optimized for separate process steps. This allows injectors to be set properly for each separate process step. For instance, a wafer can be subjected to a deposition reaction in one chamber and an etch treatment in another chamber. Injector settings are parameters typically tuned to provide uniform exposure of the substrate to gases.